Post on 14-Dec-2015
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Chemistry 8.2
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The Nature of Covalent Bonding
The colors in this map indicate the concentrations of ozone in various parts of Earth’s atmosphere. Oxygen atoms can join in pairs to form the oxygen you breathe and can also join in groups of three oxygen atoms to form ozone.
8.2
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The Nature of Covalent Bonding
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8.2 The Octet Rule in Covalent Bonding
The Octet Rule in Covalent Bonding
What is the result of electron sharing in covalent bonds?
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The Nature of Covalent Bonding
>8.2 The Octet Rule in Covalent Bonding
In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases.
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The Nature of Covalent Bonding
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8.2 Single Covalent Bonds
Single Covalent Bonds
How do electron dot structures represent shared electrons?
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The Nature of Covalent Bonding
> Single Covalent Bonds
Two atoms held together by sharing a pair of electrons are joined by a single covalent bond.
8.2
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The Nature of Covalent Bonding
>8.2 Single Covalent Bonds
An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots.
A structural formula represents the covalent bonds by dashes and shows the arrangement of covalently bonded atoms.
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The Nature of Covalent Bonding
> Single Covalent Bonds
The halogens form single covalent bonds in their diatomic molecules. Fluorine is one example.
8.2
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The Nature of Covalent Bonding
>8.2 Single Covalent Bonds
A pair of valence electrons that is not shared between atoms is called an unshared pair, also known as a lone pair or a nonbonding pair.
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The Nature of Covalent Bonding
> Single Covalent Bonds
The hydrogen and oxygen atoms attain noble-gas configurations by sharing electrons.
8.2
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The Nature of Covalent Bonding
> Single Covalent Bonds
The ammonia molecule has one unshared pair of electrons.
8.2
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The Nature of Covalent Bonding
> Single Covalent Bonds
Methane has no unshared pairs of electrons.
8.2
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Section Assessment8.1
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Section Assessment
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Section Assessment
8.1
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Practice Problems
Section Assessment
Problem Solving 8.8 Solve Problem 8 with the help of an interactive guided tutorial.
for Conceptual Problem 8.1
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The Nature of Covalent Bonding
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8.2 Double and Triple Covalent Bonds
Double and Triple Covalent Bonds
How do atoms form double or triple covalent bonds?
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The Nature of Covalent Bonding
>8.2 Double and Triple Covalent Bonds
Atoms form double or triple covalent bonds if they can attain a noble gas structure by sharing two pairs or three pairs of electrons.
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The Nature of Covalent Bonding
>8.2 Double and Triple Covalent Bonds
A bond that involves two shared pairs of electrons is a double covalent bond.
A bond formed by sharing three pairs of electrons is a triple covalent bond.
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The Nature of Covalent Bonding
> Covalent Bonds
Simulation 6 Simulate the covalent bonding between molecules
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The Nature of Covalent Bonding
> Double and Triple Covalent Bonds
Each nitrogen atom has one unshared pair of electrons.
8.2
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The Nature of Covalent Bonding
> Double and Triple Covalent Bonds8.2
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The Nature of Covalent Bonding
>8.2 Double and Triple Covalent Bonds
Carbon dioxide gas is soluble in water and is used to carbonate many beverages. A carbon dioxide molecule has two carbon-oxygen double bonds.
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The Nature of Covalent Bonding
> Double and Triple Covalent Bonds
Carbon dioxide is an example of a triatomic molecule.
8.2
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The Nature of Covalent Bonding
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8.2 Coordinate Covalent Bonds
Coordinate Covalent Bonds
How are coordinate covalent bonds different from other covalent bonds?
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The Nature of Covalent Bonding
> Coordinate Covalent Bonds
In carbon monoxide, oxygen has a stable configuration but the carbon does not.
8.2
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The Nature of Covalent Bonding
>8.2 Coordinate Covalent Bonds
As shown below, the dilemma is solved if the oxygen donates one of its unshared pairs of electrons for bonding.
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The Nature of Covalent Bonding
>8.2 Coordinate Covalent Bonds
A coordinate covalent bond is a covalent bond in which one atom contributes both bonding electrons.
In a structural formula, you can show coordinate covalent bonds as arrows that point from the atom donating the pair of electrons to the atom receiving them.
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The Nature of Covalent Bonding
>8.2 Coordinate Covalent Bonds
In a coordinate covalent bond, the shared electron pair comes from one of the bonding atoms.
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The Nature of Covalent Bonding
> Coordinate Covalent Bonds
A polyatomic ion, such as NH4+, is a tightly
bound group of atoms that has a positive or negative charge and behaves as a unit.
Most plants need nitrogen that is already combined in a compound to grow.
8.2
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The Nature of Covalent Bonding
> Coordinate Covalent Bonds8.2
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Section Assessment8.2
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Section Assessment
8.2
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Section Assessment
8.2
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Practice Problems
Section Assessment
Problem-Solving 8.10 Solve Problem 10 with the help of an interactive guided tutorial.
for Conceptual Problem 8.2
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The Nature of Covalent Bonding
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Bond Dissociation Energies
Bond Dissociation Energies
How is the strength of a covalent bond related to its bond dissociation energy?
8.2
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The Nature of Covalent Bonding
> Bond Dissociation Energies
The energy required to break the bond between two covalently bonded atoms is known as the bond dissociation energy.
A large bond dissociation energy corresponds to a strong covalent bond.
8.2
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The Nature of Covalent Bonding
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Resonance
Resonance
How are oxygen atoms bonded in ozone?
8.2
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The Nature of Covalent Bonding
> Resonance
Ozone in the upper atmosphere blocks harmful ultraviolet radiation from the sun. At lower elevations, it contributes to smog.
8.2
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The Nature of Covalent Bonding
> Resonance
The actual bonding of oxygen atoms in ozone is a hybrid, or mixture, of the extremes represented by the resonance forms.
8.2
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The Nature of Covalent Bonding
> Resonance
A resonance structure is a structure that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion.
8.2
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The Nature of Covalent Bonding
>
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Exceptions to the Octet Rule
Exceptions to the Octet Rule
What are some exceptions to the rule?
8.2
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The Nature of Covalent Bonding
> Exceptions to the Octet Rule
The octet rule cannot be satisfied in molecules whose total number of valence electrons is an odd number. There are also molecules in which an atom has fewer, or more, than a complete octet of valence electrons.
8.2
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The Nature of Covalent Bonding
> Exceptions to the Octet Rule
Two electron dot structures can be drawn for the NO2 molecule.
8.2
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The Nature of Covalent Bonding
> Exceptions to the Octet Rule
NO2 is produced naturally by lightning strikes.
8.2
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The Nature of Covalent Bonding
> Exceptions to the Octet Rule
The electron dot structure for PCl5 can be written so that phosphorus has ten valence electrons.
8.2
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Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section 8.2.
8.2 Section Quiz.
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1. In covalent bonding, atoms attain the configuration of noble gases by
a. losing electrons.
b. gaining electrons.
c. transferring electrons.
d. sharing electrons.
8.2 Section Quiz.
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8.2 Section Quiz
2. Electron dot diagrams are superior to molecular formulas in that they
a. show which electrons are shared.
b. indicate the number of each kind of atom in the molecule.
c. show the arrangement of atoms in the molecule.
d. are easier to write or draw.
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3. Which of the following molecules would contain a bond formed when atoms share three pairs of electrons?
a. Se2
b. As2
c. Br2
d. Te2
8.2 Section Quiz
END OF SHOW